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require a special interface card. Data rates reach 56Kbaud, but lines can be added in parallel to increase the speed. These tend to be high cost and are less popular.

DSL - Digital Subscriber Line (DSL) - This technology uses an existing residential phone line, but at frequencies above the audio range. The network connection is always active, but telephone usage can be permitted at any time. These have a faster data transfer rate than dial up connections, but still have a higher cost.

Cable - These broadband networks provide a permanent network connection that uses existing cable television networks. Special networking hardware is required. These networks are notable because the download speeds is higher than the download speed.

Satellite - These connections are available at a high cost and are suitable for remote locations where other communications access is not possible.

Fiber - Not available yet, but should be soon in high population areas. Expect very high speed access.

4.3 INTERNET

The Internet is a collection of networking technologies, such as Ethernet, SLIP, PPP and oth-

ers that allows computers to communicate and exchange information. The concept of the Internet

began with ARPANET which was funded as a Department of Defense project in 197x. In 198x

the Internet was developed, and began to replace the ARPANET. By the late 1980s the Internet

was widespread between most universities, colleges, major companies and government agencies

around the world. Finally, the Internet hit widespread public usage by the mid 1990s. Today it is

the accepted defacto standard network in the world.

Originally the Internet was used to exchange email and files. It was common to anonymously

log into a remote computer, with FTP, and upload and download files. In the early 1990s a number

of new applications were developed to make interaction with remote computers easier. For exam-

ple ’archie’ made it easy to search for files by names. ’wais’ and ’gopher’ were early predecessors

to ’mosiac’ which then lead to ’netscape’. At that time (about 1993) the face of the internet started

to change, thanks to the World Wide Web (WWW). Non-professional users of the internet started

to arrive through the America On-Line (AOL) service. This also coincided with the first major

case of ’spam’, where a legal firm mass mailed advertisements for immigration services. Finally,

by the mid 1990s microsoft stopped referring to the Internet as a ’fad’. Today, most people and

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companies vie for an Internet presence.

This section will outline some of the core concepts that are important when designing applications that use the Internet.

4.3.1 Computer Addresses

Most users are familiar with text computer names, such as ’www.gvsu.edu’. But, these names are only for convenience, and the same computer can have multiple names. Consider the example below. The machine ’claymore.engineer.gvsu.edu’ can also be called with ’www.eod.gvsu.edu’.

In actuality, each computer on the network has a unique four number address. Both of the names below refer to the same computer with the numerical address ’148.61.104.215’. The digits of the address can range from 0 to 255.

When a text computer name is supplied it is converted to a numerical address before network access occurs. Consider the case where a computer name is typed into a web browser. The web browser will then call another computer called a Domain Name Server (DNS). The DNS computer has a database of local and remote computers names and numbers. It will convert the computer name to a number, and then return it to the web browser. The web browser then uses the computer number to connect to the named computer.

The number has four parts. The first two digits ‘148.61’ indicate to all of the internet that the computer is at ‘gvsu.edu’ (we actually pay a yearly fee to register this). The third number indicates what LAN the computer is located on (Basically each sub-network has its own number). Finally the last digit is specific to a machine. This addressing method makes it easy to direct net-